Python built-in functions (16) -- dir, python built-in functions dir

Python built-in functions (16) -- dir, python built-in functions dir

English document:

dir([Object])

Without arguments, return the list of names in the current local scope. With an argument, attempt to return a list of valid attributes for that object.

If the object has a method named__dir__(), This method will be called and must return the list of attributes. This allows objects that implement a custom__getattr__()Or__getattribute__()Function to customize the waydir()Reports their attributes.

If the object does not provide__dir__(), The function tries its best to gather information from the object's__dict__Attribute, if defined, and from its type object. The resulting list is not necessarily complete, and may be inaccurate when the object has a custom__getattr__().

The defaultdir()Mechanic behaves differently with different types of objects, as it attempts to produce the most relevant, rather than complete, information:

• If the object is a module object, the list contains the names of the module's attributes.
• If the object is a type or class object, the list contains the names of its attributes, and recursively of the attributes of its bases.
• Otherwise, the list contains the object's attributes 'names, the names of its class's attributes, and recursively of the attributes of its class's base classes.

 

Note:

1. If no parameter is input, a list of variables, methods, and definitions in the current scope will be returned.

>>> Dir () ['_ builtins _', '_ doc _', '_ loader _', '_ name __', '_ package _', '_ spec _'] >>> a = 10 # define variable a >>> dir () # An additional a ['_ builtins _', '_ doc _', '_ loader _', '_ name __', '_ package _', '_ spec _', 'a']

2. When the parameter object is a module, the system returns the attribute and method list of the module.

>>> import math>>> math<module 'math' (built-in)>>>> dir(math)['__doc__', '__loader__', '__name__', '__package__', '__spec__', 'acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', 'atanh', 'ceil', 'copysign', 'cos', 'cosh', 'degrees', 'e', 'erf', 'erfc', 'exp', 'expm1', 'fabs', 'factorial', 'floor', 'fmod', 'frexp', 'fsum', 'gamma', 'gcd', 'hypot', 'inf', 'isclose', 'isfinite', 'isinf', 'isnan', 'ldexp', 'lgamma', 'log', 'log10', 'log1p', 'log2', 'modf', 'nan', 'pi', 'pow', 'radians', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'trunc']

3. When the parameter object is a class, the attribute and method list of the class and its subclass are returned.

>>> Class A: name = 'class' >>>> a = A () >>> dir (a) # name is the attribute of class, others are the default inherited object attributes and methods ['_ class _', '_ delattr _', '_ dict __', '_ dir _', '_ doc _', '_ eq _', '_ format _', '_ ge __', '_ getattribute _', '_ gt _', '_ hash _', '_ init _', '_ le __', '_ lt _', '_ module _', '_ ne _', '_ new _', '_ reduce __', '_ performance_ex _', '_ repr _', '_ setattr _', '_ sizeof _', '_ str __', '_ subclasshook _', '_ weakref _', 'name']

4. When the object is definedThe _ dir _ method returns the result of the _ dir _ method.

>>> Class B: def _ dir _ (self): return ['name', 'age'] >>> B = B () >>> dir (B) # Call the _ dir _ method ['age', 'name']